Dynamic recrystallization behavior and strengthening-toughening effects in a near-α Ti-xSi alloy processed by hot extrusion

Dynamic recrystallization and strengthening-toughening effects were investigated in the processed near- Ti-xSi alloy by hot extrusion. The yielding and ultimate tensile strengths were enhanced by 138.5 MPa and 118.7 MPa in the hot-extruded Ti-Si alloy compared with pure Ti. The double GSS effects (gradient silicon solutes - gradient shearing strain) led to the bimodal microstructure (21.8 µm deformed strips and 5.2 µm recrystallized grains) and grain refinement by dragging the recrystallization nucleation and grains growth during extrusion. The yielding strength enhancement was resulted from multi-factor Si solid solution, grain refinement and oxygen solid solution. Multi-factor Si solid solution was found to be the dominant mechanism, which was a summation of size misfit, modulus mismatch, strain hardening, narrow slip band and texture strengthening. Obvious strain hardening and late necking occurrence would be positive in obtaining the excellent ultimate tensile strength. Ductility was maintained at 22.9% from strain compatibility and cracks suppression. This study may provide a new understanding on the relationship among the mechanical properties, microstructure and processing of Ti-xSi alloy.